The Science Behind Why Some People Are Left-Handed

August 13 is International Left-handers Day, a time to take a look at all things left-handed including some research that offers a different answer to an age-old question — why are some people left-handed?

Left-handed History

The Italian word for left is sinistra. If it seems familiar that is because it shares roots with the English word ‘sinister’.

Cesare Lombroso, the 19th-century Italian described as ‘the father of criminology’, wrote a paper for North American Review in 1903 in which he preached ‘what is sure is, that criminals are more often left-handed than honest men, and lunatics are more sensitively left-sided than either of the other two.’

One of the greatest Italians ever was ambidextrous but drew and painted left-handed. Art purporting to be the work of Leonardo da Vinci can be revealed as fakes by techniques that can show they were created by a right-hander.

They discovered a significant difference in gene expression in segments of the spinal cord responsible for controlling our arms and legs – the first time this has been proven.

Importantly, their research also points to epigenetics as playing an important role in this gene expression.

Epigenetics is what controls genes, it encompasses the chemical modifications your genes undergo from outside factors. Things like the food you eat, how much exercise you do or how much sleep you get.

Ocklenburg and Schmitz concluded that ‘our data strongly suggest a multifactorial model for the ontogenesis of hemispheric asymmetries, including both multiple genetic and epigenetic factors.’

Which in plain terms means that there are many factors which determine someone’s handedness and they include both genes and epigenetics.

The scientists’ findings seem to back up a 2006 study on sets of twins, which concluded that genes alone account for only 25 percent of the influence over right- or left-handedness, while the remaining 75 percent is down to epigenetics.

A More Left-handed World

While this study may not provide the conclusive proof we hoped for, it is noteworthy for discovering the significance of the spinal cord.

The research also opens up new possibilities to explore — in terms of gene and epigenetic research — potential keys to unlocking advances which would have much wider implications for humanity, such as a cure for cancer or even ageing.

While science continues to search for a unifying theory on what makes us righties or lefties, it is worth taking a moment to celebrate how much better our current world is for our left-handed brethren.

Unlike decades past, being a leftie does not have to be a major inconvenience anymore. These days there are all kinds of products designed specifically for lefties.

You May Also Like

About DCODE

From cultural oddities to unsolved mysteries, Discovery DCODE unravels the quirkiest ideas and explores the science that matters to you. Quench your thirst to make sense of the world. Satisfy your curiosity with fascinating content for a smarter you.